Expertise

Having a lava bucket in your inventory will deal 2 damage (1 heart) every 5 ticks.

Offhanding something while handling a tool will make it less efficient.

The lower your health gets, the more negative effects you get. Same goes for hunger.

After waking up, you get a couple negative effects, and your hunger goes down quite a bit.

As compensation, there’s some expert mode drops. You can find those in the Items section.

MASTER MODE IS OPTIONAL – GAMERULE FOUND IN MISC

No more saturation! What you see is now what you have.

There’s a 5% chance upon breaking a block for it to chip your tool and deal 5-15 damage to your tool, regardless of unbreaking.

The more items in your inventory, the heavier you are. Enjoy the constant slowness!

And because why not, we halved your max HP!! Now you just have 5 hearts!

Master mode also changes some things from expert.

After waking up, you lose even more hunger.

Status effects are more drastic. 

Prismatic Broadsword:

     9 base damage. Temporarily places water (if nothing is in the way) on attack. Average speed. (1.6)

Witherer:

     10 base damage. Inflicts wither on attack. Slightly faster speed. (1.7)

Dragonslayer:

     12 base damage. Inflicts poison on attack. Slightly faster speed. (1.8)